In a current mobile communication system, in order to provide a user group with better service, it is often required to combine multiple wireless resource management entities (i.e. network entities for managing a wireless resource and being responsible for access of User Equipment (UE) in a wireless access network, e.g. a cell or abase station in various mobile communication systems) into a Closed Subscriber Group (CSG) with respect to the particular user group. For example, only users within a company or school are included in a particular user group, and multiple wireless resource management entities are combined into a CSG with respect to the user group, so as to provide a specialized access service. Combining multiple wireless resource management entities into the CSG with respect to a particular user group is common in the mobile communication system. In order to explain this situation more clearly, a Long Term Evolution (LTE) system of System Architecture Evolution (SAE) is taken as an example for the explanation below.
FIG. 1 is a schematic diagram of a structure of an LTE system in the prior art. As shown in the FIG. 1, in the wireless access network of the LTE system, the wireless resource management entity includes a macro base station (eNB) 102 and a home base station (HeNB) 103, and a home base station gateway (HeNB GW) 104 is optionally included in the wireless access network. The eNB 102 can be directly connected with a Mobile Management Entity (MME) 105 in a core network. When the HeNB GW 104 is included in the wireless access network, the HeNB 103 is connected with the MME 105 through the HeNB GW 104. When the HeNB GW 104 is not included in the wireless access network, the HeNB 103 can be directly connected with the MME 105.
For the wireless resource management entity in the LTE system, in order to provide more access, multiple types of HeNBs, which include an opened type, a hybrid type and a CSG type, are provided in the prior art, taking the HeNB as an example. Specifically, there is no particular accessed user group for the HeNB of the opened type, and any UE can have the access. The HeNB of the CSG type is just the HeNB used by the above-mentioned user group constructed by all the users inside a company or school, and allows only the UE in the particular user group (in order to facilitate description, the UE in the particular user group is briefly referred to as CSG UE in the following) served by it to have the access. The HeNB of the hybrid type not only constructs the CSG with another HeNB to allow the CSG UE served by it to have the access so as to provide a much better access service with respect to the CSG UE, but also can allow another non-CSG UE (a UE that does not belong to the CSG) to have the access.
It can be seen from the above description that in the existing mobile communication system, for the wireless resource management entity, not only multiple wireless resource management entities can construct the CSG to provide the wireless resource management entity of the CSG type, e.g. the HeNB of the CSG type, but also the wireless resource management entity of the hybrid type, e.g. the HeNB of the hybrid type, can be used to provide more access services. Meanwhile, the eNB can also support a function of the CSG, or be used as the eNB of the hybrid type when supporting the function of the CSG.
In the prior art, at any time that the UE moves between the HeNBs (or between the eNB and the HeNB), an S1 handover process is performed. As shown in FIG. 2, it is easy to understand that an optional process description already known by those skilled in the art is omitted in the following, and the S1 handover process mainly includes:
Step 201: A S-(H)eNB as a source eNB or HeNB transmits a handover requirement message to the HeNB gateway (GW).
Step 202: The HeNB GW transmits the handover requirement message to the MME.
Step 203: The MME transmits a handover request message to the HeNB GW, and the HeNB GW transmits the handover request message to a T-(H)eNB as a destination eNB or HeNB.
Step 204: The T-(H)eNB allocates the resource and transmits a handover request acknowledgement message to the HeNB GW, and the HeNB GW transmits the handover request acknowledgement message to the MME.
Step 205: The MME transmits a handover command message to the HeNB GW, and the HeNB GW transmits the handover command message to the S-(H)eNB.
Step 206: The S-(H)eNB transmits a handover command message to the UE.
Step 207: The UE is synchronized with a destination cell, and transmits a handover acknowledgement message to the T-(H)eNB.
Step 208: The T-(H)eNB transmits a handover notification message to the HeNB GW, and the HeNB GW transmits the handover notification message to the MME.
Step 209: The MME transmits a bearer update request message for bearer modification to a Serving Gateway/Packet Data Network Gateway (S-GW/PDN GW) (here, a signaling procedure between the S-GW and the PDN GW is omitted). Specifically, the S-GW mainly provides the function of a user plane. The PDN GW is responsible for the function such as billing, lawful interception, and such. According to context information of the UE, if the PDN GW requests the UE to report a position and/or CSG information of the user, the MME causes an information element of the CSG of the user and the position of the UE to be included in the bearer update request message.
Step 210: The S-GW/PDN GW transmits a bearer update response message to the MME.
Step 211: The UE initiates a Trunk Access Unit (TAU) process.
Step 212: The MME transmits a UE context release command message to the HeNB GW, and the HeNB GW transmits the UE context release command message to the S-(H)eNB.
Step 213: The S-(H)eNB transmits a UE context release completion message to the HeNB GW, and the HeNB GW transmits the UE context release completion message to the MME.
The S-(H)eNB and the T-(H)eNB in FIG. 2 are used in order to allow the procedure described above to be applied to the S1 handover when the UE moves between the eNBs or moves between the eNB and the HeNB. Therefore, the S-eNB represents a source eNB, the T-eNB represents a target (i.e. destination) eNB, while the S-HeNB represents the source HeNB and the T-HeNB represents the destination HeNB. When the S-(H)eNB or the T-(H)eNB is the macro base station eNB, the HeNB GW does not exist, and the S-(H)eNB or the T-(H)eNB communicates with the MME.
It can be found that when an amount of the HeNB (or the eNB) is relatively large, if the handover method described above is used and the UE carries out every handover between the HeNBs or the eNBs using the S1 handover, the core network may suffer an extremely heavy burden, thus an efficiency of the handover is greatly decreased.
In this situation, performing the handover using an X2 interface is a feasible alternative solution. However, there is no solution at present that the HeNB uses the X2 handover in the prior art. If only an existing X2 handover process is used for the HeNB, complexity of the HeNB may be increased. If an architecture of the X2 interface is used between the GWs or between the GW and the eNB, how to establish the X2 interface between the GWs or between the GW and the eNB is also a pending problem in the prior art. In addition, in performing the X2 handover using the GW, there are also some security problems that an existing security mechanism cannot address.